As a combustion burner for combusting pulverized coal fuel, there is known a burner where a plurality of flame holders, which are referred to as “splitters”, are disposed at an outlet of a fuel nozzle of the burner. In the burner, a recirculation region is formed on a downstream side of the splitters to maintain combustion of pulverized coal. In this manner, ignition and flame holding (hereinafter referred to as “internal ignition” or “internal flame holding”) are performed in the vicinity of a center axis of the fuel nozzle so that reduced combustion is performed under an air deficiency condition to realize low NOx combustion.
To enhance flame holding performance, it is preferable that a flame holder have a long edge length of splitter length. However, when the number of splitters is increased, a blocking rate of an outlet of a burner and hence, pressure loss of the burner is increased. Further, even when the number of splitters is increased while reducing a width of the splitters so as to ensure the edge length of splitter length, the splitters are disposed close to a wall portion of the fuel nozzle and hence, there is a possibility that ignition occurs at an outer periphery of the fuel nozzle. A combustion air supply nozzle and the like are disposed outside the fuel nozzle so that a large amount of oxygen is present, and therefore when external ignition occurs, there is a risk that a large amount of NOx is generated.
The following PTL 1 and PTL 2 disclose combustion burners where splitters are formed into a comb shape when the splitters are viewed in a front view from the downstream side.